1. Field of the Invention
The present invention relates to a compressor, and more particularly to a compressor including an oil residue pool provided, in an oil pump that sucks up oil from an oil storage in the bottom, to allow part of return oil to reside in the pool when the compressor stops.
2. Description of the Related Art
In general, known compressors for use in compression of gases may be of the reciprocation type, the rotary type and the scroll type. These compressors comprise an electric element including an electric motor, and a compressive element driven by the electric element. They are operative to compress a gas such as a refrigerant gas led into the compressive element and discharge the compressed gas, which is fed to an air conditioner, a refrigerator, or a freezer/refrigerator in a freezing cycle.
The compressors of such the types generally include an oil storage to store lubricant oil in the bottom of a container that configures a compressor body. An oil pump is attached to the lower end of a driveshaft axially installed on the rotor of the electric element. This oil pump is operative to suck up the oil from the oil storage and supply the oil to a sliding portion of the compressive element and a bearing portion of the driveshaft for lubrication through an oil passage provided in the driveshaft along the axial line. The oil once used in lubrication is fed back to the oil storage and reused repeatedly in this structure (see Patent Document 1 (JP-A 6-26469), Patent Document 2 (JP-A 9-32760), and Patent Document 3 (JP-A 5-65884), for example).
There is another oil pump structured as shown in FIG. 6(a). This oil pump comprises a support frame A attached to a compressor container. Together with an attachment member B, a cylinder D is fixed to the support frame A using a bolt C. A driveshaft E is axially installed on a rotor of an electric element (not shown). A rotator G is axially installed on the lower end of the driveshaft E via a pin F and operative to rotate within an inner space Da of the cylinder D. A suction pipe I is provided, which has an upper end connected to a communication notch H formed by notching part of the cylinder D, and the other end inserted and arranged in an oil storage (not shown) provided in the container bottom.
The cylinder D of this oil pump is provided with plates J, K located in the upper and lower surfaces thereof to close the upper and lower surfaces of the inner space Da. In addition, the cylinder is attached such that the center of the inner space Da is slightly deviated W from the center of the rotator G to form an eccentric annular oil passage between the cylinder and the rotator G as shown in FIG. 6(b). This oil passage is brought into communication with the communication notch H and a communication path Ba formed in the upper surface of the attachment member B as shown in FIG. 6(a). The communication path Ba is brought into communication with an axial bore Ga formed through the center of the rotator G. A notch Gb is provided in the outer circumference of the rotator G. A columnar piston member L is slidably fitted in the notch Gb.
In the oil pump thus configured, when the driveshaft E rotates about the axis, the rotator G rotates within the inner space Da of the cylinder D. As a result, a suction force is caused in the communication notch H and it sucks up the oil from the oil storage through the suction pipe I. The oil sucked up through the suction pipe I is sucked from the communication notch H into the inner space Da of the cylinder D. In addition, the oil pushed by the piston member L moves through the eccentric annular oil passage and flows into the communication path Ba of the attachment member B. Then the oil moves upward from the communication path Ba along the inner wall of the axial bore Ga in the rotator G. It further moves upward along the inner wall of the oil passage Ea provided inside the driveshaft E and is supplied to the sliding portion of the compressive element and the bearing portion of the driveshaft E.
In the above conventional oil pump, a centrifugal force caused from the rotation of the driveshaft E about the axis makes the oil move upward along the inner wall of the oil passage Ea. The oil is then supplied from the oil supply hole provided in communication with the oil passage Ea to the sliding portion of the compressive element and the bearing portion of the driveshaft. When the compressor stops, the centrifugal force caused by the driveshaft E is lost and the oil in the oil passage Ea moves downward along the inner wall. Under pressure of the oil moving downward, the oil flows backward through the flow path in the oil pump and drops from the communication notch H through the suction pipe I into the oil storage. Therefore, when the compressor stops, the oil is hardly allowed to reside in the oil pump. This causes a problem because the oil supply performance of the oil pump is lowered when the compressor restarts.